1. Field of the Invention
The present invention relates to a method for estimating a splice loss of a spliced section of a fusion-spliced optical fiber.
2. Description of the Related Art
Conventionally, the splice loss of a spliced section of an optical fiber is measured by a power monitor method. According to this method, light is permitted to pass through the optical fiber via the spliced section and the splice loss of the spliced section is measured from the amount of light received.
Due to the necessity to permit light to pass through an optical fiber, however, the power monitor method has a low operability. In this respect, therefore, an outline monitor method has recently been used frequently for its higher operability. (D. Marcuse "Loss Analysis of Single Mode Fiber Splices", BSTJ, Vol. 56, No. 5, 1977; Satoru Yamazaki et al. "Simple Splicing Method for Single Mode Optical Fiber", National Conversation Record No. 2108, 1987, The Institute of Electronics Information And Communication Engineers; Akihiko Ishikura et al. "Splice Loss Factor Analysis for Subscriber Single-Mode Fibers", National Conversation Record No. 2100, 1987, The Institute of Electronics Information And Communication Engineers; Atsushi Ide et al. "Loss Assurance Method for SM-Fiber Mass-Splice Using Image Measurement", National Conversation Record NO. 2101, 1987, The Institute of Electronics Information And Communication Engineers). According to the Yamazaki et al. method, light is irradiated on the spliced section from two directions, X and Y, normal to each other to pick up an X image and a Y image of the outline of the spliced section, and the splice loss is acquired from the X and Y images. According to the conventional method for measuring a splice loss by monitoring the outline of a spliced section, however, a splice loss originated from opposite-phase core distortion cannot precisely be measured although a splice loss caused by axial deviation or angular deviation can be measured with a certain accuracy.